Steel sections and steel piling often require splitting along their lengths to provide a desired shape of section. For example, by splitting an “I” beam along the longitudinal centre line of the web thereof, a pair of “T” sections can be produced. Similarly, by splitting a box section along the longitudinal centre line thereof, a pair “U” shaped channel members can be produced. Many other shapes can be produced by starting with differently shaped products including double rolled sections, for instance bulb flats, conventional flats, grader bars and channels can all be double rolled and then split along their lengths.
Traditionally, oxy-propane or oxy-acetylene torches have been used to split elongate steel members longitudinally. When splitting a member using such torches it is common practice when commencing splitting to cut the member at spaced apart intervals in order to avoid the halves of the member bowing outwards or inwards. This practice is known as stitching. As a secondary operation, the stitches (which are short in comparison with the cuts) are removed, again using and oxy-propane or oxy-acetylene torch. Using these torches poses a number of problems. Firstly, the separating process is slow and requires a significant amount of labour. Secondly, the operation is dangerous. Occasionally, the stitches holding the member together are too weak to withstand the internal stresses in the member created during its manufacture. If this is so, the member may break the stitches and spring outward or inward without warning. Such an event could result in injury or loss of life. Thirdly, heat generated during separation accentuates any inherent tendency in the member to bend during separation. Fourthly, the finish on the separated edges is of a low standard and often requires milling to establish an edge that can be welded to.
In order to overcome the problem of speed of operation, and quality of finish plasma guns have been introduced. However, these still often use the “stitching” technique Additionally, plasma guns operate at higher temperatures than do flame cutters, i.e. oxy-propane or oxy-acetylene torches. Whilst less dross and slag is produced during separation with plasma cutting compared to flame cutting, the resulting edges must nevertheless be dressed. The heat generated during flame and plasma cutting also causes metallurgical changes to the steel in the region of the cut. In plasma cutting the region can extend 5 mm to 15 mm to either side of the cut along the full length thereof, whereas in flame cutting the metallurgical changes extend further but are less marked. As the steel cools, or when it is straightened cracking can occur. These metallurgical changes are unacceptable, and because of this, the industry will not permit the splitting of members having a web thickness of 20 mm or greater using plasma guns or flame cutting.
In terms of rolling steel, it can be advantageous to double roil sections, i.e. two angles are rolled as a channel. This is because the throughput of the mill is increased, and therefore its costs of production are decreased. It is known to split double rolled sections in half by snapping the section in two along a line of weakness. For example, angles may be formed by splitting a channel along a longitudinal line of weakness. The problem with sections produced by double rolling and splitting them in the manner described is that the finish is extremely poor.
In U.S. Pat. No. 5,033,610 a support station is described, the station being used to support workpieces shaped as U-, I-, L-, T- or circular profiles, whilst they are cut using a flame cutter. The workpieces are cut to length, rather than longitudinally.
In U.S. Pat. No. 4,693,761 a device and process for cutting or welding profiles using a robot having a cutting torch attached thereto is described. The device and process are used for cutting profiles to length, rather than for cutting them longitudinally.